Hey guys I have an 01 Civic ex vtec obviously. The car was a vtec car from the factory however someone put a non vtec base model motor in it. Recently it popped the head gasket. So I pulled the head replaced the gasket and put a VTEC head on the car since the harness was all still intact and fine. I fired it up a after the head gasket job let it sit and idle and after about 3 minutes of it running it died. Went to start it back up and the immobilizer key is flashing. Well I got to looking and forgot to snug up that ground that runs from the wiring harness to next to the t-star housing. So I snugged it up and thought maybe I fried the ecm leaving it loose. So I went to the junkyard and pulled an ecu out of an 01 Civic ex 2dr automatic because that's what my car is. Replaced ecu and I towed it to the dealer to have them program it yesterday, they programmed it and said it fired up twice ran great and died after about 10 seconds just like they shut the key off. They didn't know what was wrong with it. So I brought it home and once again every once in a while it will Fire up and run great for about 10 seconds but die, go to crank on it again and they immobilizer lifht is flashing. Anyone ever heard of or seen this happen? Any tips or ideas would be appreciated the dealer also told me to double check I got the ecm out of an 01 civic ex 2 dr vtec with power locks and windows and I did double check that because I pulled it myself. that's the answer they had for me

 

If the immobilizer light is going off, it would appear as though there's something within that system (be it the immobilizer transponder, ring, or in the ECU itself) that is malfunctioning.

 

update. a good friend of mine owns a junkyard, he got an 01 civic ex 2 door car exactly like mine just different color in it ran so I pulled the steering column and ecm out of it and put it in my car so the key would match the ecm, put it in it took about a half hour and boom as soon as I turn the key on the immobilizer light is flashing and wont start it just cranks. also put a new battery in it yesterday. where do the ignition get ground from? I also wire wheeled the ground from the radiator support to the engine and the g101 ground that goes from the wiring harness to the t stat housing. also when you turn the key on you can take the car out of PARK without pressing the brake. im just lost and need help please